The production of alcoholic spirits involves an aging step. During the aging step, wooden barrels hold the alcohol spirits, and the wood imparts a distinct flavor to the spirits. Colder temperatures at night cause the pores of the wooden barrels to close, and higher temperatures during day cause the pores to open. Over a period of years, the opening and closing of the pores of the wooden barrels circulates the spirits in and out of the barrel wood. The barrel during toasting is impregnated with aromatic aldehydes which impart flavor to the spirits during this circulation or breathing process. For scotch whiskey, aging may last up to twelve or even eighteen years. Some barrels may be reused. In the production of bourbon and wine, a barrel may only be used once.
The distinctive flavor imparted to spirits during aging results from the wood itself and pre-treatment of the inside surfaces of the barrels during manufacture. This pretreatment includes at least two steps. The first step involves manufacturing the barrels in a steam tunnel to increase the moisture content of the wooden staves which form the barrel. The increased moisture content facilitates longitudinal bending of the staves, which is required to form a barrel shape. Once manufactured, the inside surfaces of the barrels must be roasted. The moisture content helps reduce burning during roasting.
Current barrel roasters utilize direct flame impingement upon the inside surface of the barrel. This is accomplished by indexing each barrel over an upwardly directed gas burner. The flame from the burner enters one open end of the barrel and exits at the other end of the barrel. Most barrel roasting of this type last for about fourteen minutes, with the flame set for a temperature of about at least 2,000.degree. F.
This method of roasting barrel suffers from a number of disadvantages. Primarily, the use of direct flame impingement upon the inside surfaces of the barrel produces nonuniform roasting from top to bottom. Because the flame is closest to the bottom, the bottom end of the barrel may become burnt while the top end may be insufficiently roasted. The desired result for aging is a uniform roast. Sometimes roasting is referred to as charring or toasting of the wood. In the context of this application, the word "char" is equivalent to the word "roast," and it does not refer to burning or blackening of the staves due to too much roasting.
In addition to nonuniformity, roasting by direct flame impingement commonly produces inconsistencies from barrel to barrel. While inconsistency from barrel to barrel may be correctable by controlling the flame, this has not occurred in practice, perhaps due to the expense involved. Additionally, flame control will not solve the problem of nonuniform roasting.
Finally, the use of a direct flame which can extend up to two feet beyond the top end of the barrel represents a substantial energy expense, particularly in view of the other deficiencies associated with this method.
The traditional nature of the spirit manufacturing industry has tended to discourage the changing or modification of prior methods for roasting the inside surfaces of aging barrels.
Nevertheless, it is an objective of this invention to increase uniform consistency in roasting the inside surfaces of barrels used in aging alcoholic of spirits.
It is another objective of this invention to reduce the energy costs of uniformly roasting the inside surface of a barrel used for aging alcoholic spirits.
The objectives of the invention are met by directing a stream of heated air through the barrel for a sufficient time duration to uniformly roast the entire inside surface of the barrel. The heated air should have a temperature in the range of about 650.degree. F. to 750.degree. F. The time duration for heating the barrel should be about fourteen minutes, although this time duration could probably be lowered.
Unlike direct flame impingement, a stream of heated air does not produce burning of the staves at one end of the barrel and insufficient roasting at the other end of the barrel. The use of a controlled stream of heated air provides uniformity in the roasted char along the length of the barrel.
Additionally, because the degree of certainty with which a direct stream of heated air can be controlled, the use of heated air stream results in consistent roasting from barrel to barrel. This factor is critical to the whiskey and wine industry, where uniformity in the quality of the final product is essential.
In one manner of forming the method of this invention, the heated stream of air may be directed into one, open end of the barrel from a conduit outlet. A deflector at an opposite end of the barrel partially impedes outflow of the stream from the barrel. This increases the residence time of the heated air stream within the barrel and produces more efficient and uniform roasting. If desired, steam may be injected into the air stream prior to outflow from the conduit. This step may be used to reduce the moisture loss of the barrels during roasting.
In a preferred embodiment of the invention, a barrel roasting apparatus simultaneously roasts the inside surfaces of a plurality of barrels. The apparatus includes a conveyor, a blower communicating with an air conduit, a gas burner located within the conduit, a plurality of conduit outlets located below the conveyor, a vertically movable exhaust hood located above the conveyor and a plurality of deflectors mounted to the exhaust hood.
The conveyor supports and moves the plurality of barrels horizontally into alignment with the plurality of outlets. The exhaust hood moves downwardly toward the barrels to place the deflectors at the top ends of the barrels. In this position, each barrel has an outlet directed into its open bottom end and a deflector located at its top end. The gas burner heats an air stream forced through the conduit by the blower. The heated air stream flows upwardly from the outlets and into the bottom ends of the barrels for a predetermined time duration. The deflectors at the top ends of the barrels partially impede outflow to increase the residence time of the air within the barrels and produce uniform roasting. After flowing through perforations in the deflectors or out the bottom of the barrel, the exhaust hood recovers the heated air and returns it to the conduit.
A steam injector may be located in the conduit between the gas burner and the outlets. Injecting steam into the heated air stream will reduce the moisture loss of the barrels during roasting.
After a predetermined time duration which sufficiently and uniformly roasts the entire inside surfaces of the barrels, the hood is moved upwardly and the conveyor moves a batch of roasted barrels away from the outlet and moves an unroasted batch of barrels into alignment with the outlets.
To eliminate the need to turn off the blower and the gas burner each time a roasted batch of barrels is conveyed away from the outlets and a new batch of barrels is conveyed to the outlets, the apparatus may include a bypass line which bypasses the conduits and the exhaust hood. The bypass line and each of the outlets is preferably equipped with a damper. A controller may be used to coordinate simultaneous opening of the dampers in the outlet lines and closing of the damper in the bypass line when a batch of barrels are in position between the outlets and the deflectors and ready to be roasted. Thereafter, when the barrels have been roasted for a predetermined duration, the controller simultaneously closes the dampers to the outlets and opens the damper to the bypass line.
The exhaust hood reclaims most of the heated air stream for recirculation. Also, fresh air at the inlet may be preheated by heat recovered from the exhaust air, via a fume incinerator. Compared to prior direct flame impingement roasters, this apparatus significantly reduces the total amount of energy expended in roasting barrels for use in aging whiskey and wine.
By controlling and/or varying parameters of the roasting operation such as steam injection, temperature, flow rate, pressure and duration of roasting, batches of barrels may be roasted in a manner which produces particular characteristics which are desirable because they impart a distinct flavor to a whiskey or a wine. It is believed that these parameters may be controlled to produce barrels with char characteristics which simulate the particular char characteristics common to barrels produced in various wine growing regions of France, but at a substantially lower cost.